<!doctype html><html lang="en" class="no-js"><head><meta charset="utf-8"> <!-- begin SEO --><title>DP-Mix: Differentially Private Routing in Mix Networks - Mahdi Rahimi</title><meta property="og:locale" content="en-US"><meta property="og:site_name" content="Mahdi Rahimi"><meta property="og:title" content="DP-Mix: Differentially Private Routing in Mix Networks"><link rel="canonical" href="https://mmaahhddii1995.github.io/publication/DPMix.md"><meta property="og:url" content="https://mmaahhddii1995.github.io/publication/DPMix.md"><meta property="og:description" name="description" content="Mixnets, as overlay networks, ensure anonymity for messages by forwarding them through intermediary nodes that obscure their traffic patterns from network-level adversaries. Nonetheless, the selection of intermediaries is traditionally performed uniformly at random, resulting in optimal routes being chosen no more frequently than suboptimal ones. This often causes messages to traverse inefficient paths that degrade performance or weaken security. While there have been proposals to improve route selection in mixnets, they are limited to latency reduction and rely on heuristic strategies that lack formal anonymity guarantees. To bridge this gap, we develop a framework for differentially private routing in mixnets aimed at general-purpose optimization. In this framework, each candidate route is assigned an optimality score, and routes are then selected to favor high-scoring paths while preserving anonymity under a pure differential privacy guarantee. We instantiate this model for optimizing path security, enhancing reliability, and minimizing communication latency. Additionally, we introduce a gradient-based algorithm applied post hoc to the route selection process—without weakening privacy guarantees—to prevent the over-selection of particular nodes, which could otherwise lead to security vulnerabilities or network congestion."><meta property="og:type" content="article"><meta property="article:published_time" content="2025-12-20T00:00:00+00:00"> <script type="application/ld+json"> { "@context" : "http://schema.org", "@type" : "Person", "name" : "Mahdi Rahimi", "url" : "https://mmaahhddii1995.github.io", "sameAs" : null } </script> <!-- end SEO --><link href="https://mmaahhddii1995.github.io/feed.xml" type="application/atom+xml" rel="alternate" title="Mahdi Rahimi Feed"> <!-- http://t.co/dKP3o1e --><meta name="HandheldFriendly" content="True"><meta name="MobileOptimized" content="320"><meta name="viewport" content="width=device-width, initial-scale=1.0"> <script> document.documentElement.className = document.documentElement.className.replace(/\bno-js\b/g, '') + ' js '; </script> <!-- For all browsers --><link rel="stylesheet" href="https://mmaahhddii1995.github.io/assets/css/main.css"> <!-- Custom CSS to force white background and black text --><link rel="stylesheet" href="https://mmaahhddii1995.github.io/assets/css/custom.css"> <!-- Force moon (dark mode) as default on page load --> <script> if (!localStorage.getItem('theme')) { document.documentElement.setAttribute('data-theme', 'light'); localStorage.setItem('theme', 'light'); } </script><meta http-equiv="cleartype" content="on"> <!-- start custom head snippets --> <!-- favicon from https://commons.wikimedia.org/wiki/File:OOjs_UI_icon_academic-progressive.svg --><link rel="apple-touch-icon" sizes="180x180" href="https://mmaahhddii1995.github.io/images/apple-touch-icon-180x180.png"/><link rel="icon" type="image/svg+xml" href="https://mmaahhddii1995.github.io/images/favicon.svg"/><link rel="icon" type="image/png" href="https://mmaahhddii1995.github.io/images/favicon-32x32.png" sizes="32x32"/><link rel="icon" type="image/png" href="https://mmaahhddii1995.github.io/images/favicon-192x192.png" sizes="192x192"/><link rel="manifest" href="https://mmaahhddii1995.github.io/images/manifest.json"/><link rel="icon" href="/images/favicon.ico"/><meta name="theme-color" content="#ffffff"/><link rel="stylesheet" href="https://mmaahhddii1995.github.io/assets/css/academicons.css"/> <!-- Support for MatJax --> <script src="https://cdnjs.cloudflare.com/polyfill/v3/polyfill.min.js?features=es6"></script> <script id="MathJax-script" async src="https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-mml-chtml.js"></script> <!-- end custom head snippets --></head><body> <!--[if lt IE 9]><div class="notice--danger align-center" style="margin: 0;">You are using an <strong>outdated</strong> browser. Please <a href="http://browsehappy.com/">upgrade your browser</a> to improve your experience.</div><![endif]--><div class="masthead"><div class="masthead__inner-wrap"><div class="masthead__menu"><nav id="site-nav" class="greedy-nav"> <button><div class="navicon"></div></button><ul class="visible-links"><li class="masthead__menu-item masthead__menu-item--lg persist"> <a href="https://mmaahhddii1995.github.io/">Mahdi Rahimi</a></li><li class="masthead__menu-item"> <a href="https://mmaahhddii1995.github.io/">Home</a></li><li class="masthead__menu-item"> <a href="https://mmaahhddii1995.github.io/about/">About</a></li><li class="masthead__menu-item"> <a href="https://mmaahhddii1995.github.io/cv/">CV</a></li><li class="masthead__menu-item"> <a href="https://mmaahhddii1995.github.io/publications/">Publications</a></li><li class="masthead__menu-item"> <a href="https://mmaahhddii1995.github.io/students/">Teaching & Supervision</a></li><li class="masthead__menu-item"> <a href="https://mmaahhddii1995.github.io/NEWS/">Recent News</a></li><!-- Theme toggle removed to force permanent white/black mode --></ul><ul class="hidden-links hidden"></ul></nav></div></div></div><div id="main" role="main"><div class="sidebar sticky"><div itemscope itemtype="http://schema.org/Person"><div class="author__avatar"> <img src="https://mmaahhddii1995.github.io/images/profile.png" class="author__avatar" alt=""></div><div class="author__content"><h3 class="author__name"></h3><p class="author__bio">Academic researcher in anonymous communications, privacy-preserving systems, and applied cryptography.</p></div><div class="author__urls-wrapper"> <button class="btn btn--inverse">Follow</button><ul class="author__urls social-icons"> <!-- Font Awesome icons / Biographic information --><li class="author__desktop"><i class="fa-solid fa-location-dot icon-pad-right" aria-hidden="true"></i>Leuven, Belgium</li><li class="author__desktop"><i class="fas fa-fw fa-building-columns icon-pad-right" aria-hidden="true"></i>COSIC, KU Leuven</li><li><a href="mailto:mahdi.rahimi@esat.kuleuven.be"><i class="fas fa-fw fa-envelope icon-pad-right" aria-hidden="true"></i>Email</a></li><!-- Font Awesome and Academicons icons / Academic websites --><li><a href="https://scholar.google.com/citations?user=cwhrpkQAAAAJ&hl=en"><i class="ai ai-google-scholar icon-pad-right"></i>Google Scholar</a></li><li><a href="https://orcid.org/0009-0003-0223-9082"><i class="ai ai-orcid ai-fw icon-pad-right"></i>ORCID</a></li><!-- Font Awesome icons / Repositories and software development --><li><a href="https://github.com/Mmaahhddii1995"><i class="fab fa-fw fa-github icon-pad-right" aria-hidden="true"></i>GitHub</a></li><!-- Font Awesome icons / Social media --><li><a href="https://www.linkedin.com/in/mahdirahimi95"><i class="fab fa-fw fa-linkedin icon-pad-right" aria-hidden="true"></i>LinkedIn</a></li></ul></div></div></div><article class="page" itemscope itemtype="http://schema.org/CreativeWork"><meta itemprop="headline" content="DP-Mix: Differentially Private Routing in Mix Networks"><meta itemprop="description" content="Mixnets, as overlay networks, ensure anonymity for messages by forwarding them through intermediary nodes that obscure their traffic patterns from network-level adversaries. Nonetheless, the selection of intermediaries is traditionally performed uniformly at random, resulting in optimal routes being chosen no more frequently than suboptimal ones. This often causes messages to traverse inefficient paths that degrade performance or weaken security. While there have been proposals to improve route selection in mixnets, they are limited to latency reduction and rely on heuristic strategies that lack formal anonymity guarantees. To bridge this gap, we develop a framework for differentially private routing in mixnets aimed at general-purpose optimization. In this framework, each candidate route is assigned an optimality score, and routes are then selected to favor high-scoring paths while preserving anonymity under a pure differential privacy guarantee. We instantiate this model for optimizing path security, enhancing reliability, and minimizing communication latency. Additionally, we introduce a gradient-based algorithm applied post hoc to the route selection process—without weakening privacy guarantees—to prevent the over-selection of particular nodes, which could otherwise lead to security vulnerabilities or network congestion."><meta itemprop="datePublished" content="December 20, 2025"><div class="page__inner-wrap"><header><h1 class="page__title" itemprop="headline">DP-Mix: Differentially Private Routing in Mix Networks</h1><p>Published in <i>Annual Computer Security Applications Conference (ACSAC)</i>, 2025</p></header><section class="page__content" itemprop="text"><p>The contents above will be part of a list of publications, if the user clicks the link for the publication than the contents of section will be rendered as a full page, allowing you to provide more information about the paper for the reader. When publications are displayed as a single page, the contents of the above “citation” field will automatically be included below this section in a smaller font.</p><p style="font-size: smaller">Recommended citation: M. Rahimi, “DP-Mix: Differentially Private Routing in Mix Networks,” to appear in ACSAC 2025: 41st Annual Computer Security Applications Conference, IEEE. <br /><a href="http://mmaahhddii1995.github.io/files/DP_Mix_paper.pdf">Download Paper</a> | <a href="http://mmaahhddii1995.github.io/files/DP_Mix_slides.pdf">Download Slides</a> | <a href="http://mmaahhddii1995.github.io/files/DP_Mix_bib.bib">Download Bibtex</a></p></section><footer class="page__meta"></footer><section class="page__share"><h4 class="page__share-title">Share on</h4><a href="https://bsky.app/intent/compose?text=https://mmaahhddii1995.github.io/publication/DPMix.md" class="btn btn--bluesky" title="Share on Bluesky"><i class="fab fa-bluesky" aria-hidden="true"></i><span> Bluesky</span></a> <a href="https://www.facebook.com/sharer/sharer.php?u=https://mmaahhddii1995.github.io/publication/DPMix.md" class="btn btn--facebook" title="Share on Facebook"><i class="fab fa-facebook" aria-hidden="true"></i><span> Facebook</span></a> <a href="https://www.linkedin.com/shareArticle?mini=true&url=https://mmaahhddii1995.github.io/publication/DPMix.md" class="btn btn--linkedin" title="Share on LinkedIn"><i class="fab fa-linkedin" aria-hidden="true"></i><span> LinkedIn</span></a> <a href="https://x.com/intent/post?text=https://mmaahhddii1995.github.io/publication/DPMix.md" class="btn btn--x" title="Share on X"><i class="fab fa-x-twitter" aria-hidden="true"></i><span> X (formerly Twitter)</span></a></section><nav class="pagination"> <a href="https://mmaahhddii1995.github.io/publication/VSS/" class="pagination--pager" title="On Round-Optimal Computational VSS ">Previous</a> <a href="https://mmaahhddii1995.github.io/publication/OptiMix.md" class="pagination--pager" title="OptiMix: Scalable and Distributed Approaches for Latency Optimization in Modern Mixnets ">Next</a></nav></div></article></div><div class="page__footer"><footer> <!-- Sitemap & follow removed --> <!-- Footer removed --></footer></div><script src="https://mmaahhddii1995.github.io/assets/js/main.min.js"></script></body></html>
